The document discusses various types of impurities that can be present in pharmaceutical preparations and their sources. It describes six main types of impurities: 1) those that cause toxic or adverse reactions, 2) those that deteriorate the activity of the substance, 3) those that cause incompatibility, 4) those that cause technical problems, 5) those arising from humidity/temperature, and 6) those arising from coloring/flavoring substances. Potential sources of impurities discussed include raw materials, starting materials/reagents, solvents, equipment, intermediates generated during synthesis, and manufacturing defects. Proper control of sources like raw materials, processes, storage conditions, and packaging can help minimize impurities in pharmaceutical preparations.

1. 1
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Impurities
Impurities defined as a foreign particle that affects the purity of a substance.
Usually, impurities occurring in many pharmaceutical or medicinal preparations
may be of the following types.
1. Foreign particle that bring about adverse or toxic reactions when present in
excess beyond their limits.
Example: lead, heavy metals, arsenic etc.
2. Impurities which may not cause toxic effects but bring about deterioration of
the activity of chemical.
Example: hard soap containing excess of water.
3. Impurities that cause incompatibility of active ingredient with other
substanceor which reduce the properties of active ingredient.
4. Impurities which may lead to technical problems in the applications of the
substance.
Example: presence of carbonate in ammonia solution, presence of KIO3 in KI
solution.
5. Impurities arising due to humidity temperature.
Example: presence of very low amount of moisture may enable substance to get
oxidized easily or may reduce its free flowing characteristics.
6. Impurities arising due to colouring and flavoring substances. These
impurities can be detected by changes in colour, odour, taste and
appearance.

2. 2
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Examples: Presences of phenolic compounds decolourize sodium salicylate,
presence of minute quantities of magnesium salt causes dampening of sodium
chloride.
7. Impurities which may alter the physical and chemical properties of the
substance.
8. Impurities which decrease the shelf – life.
Source of impurities
Raw materials conditions of storage packing errors
Method / process atmospheric deliberate adulteration
Starting material or Reagents careless storage
Reagents employed to eliminate other impurities filthy matter
Solvents or vehicles used in the manufacturing effect of container materials
Equipment used in the process ofmanufacturing
Intermediates generated during the synthesis
Chemical method used in the manufacturing process
Defects in the process ofmanufacturing
Manufacturing hazards

3. 3
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Raw materials:
Generally, most of the raw materials used in the manufacturing of pharmaceutical
products are naturally occurring substances. Traces of the elements present in the
raw materials may get carried to the final preparation.
Pharmaceuticalpreparation Raw materials Impurities present
Sodium compounds Sodium chloride rock
salt
Chlorides, Ca and Mg
Bismuth compounds Bismuth salts Lead, copper, and silver
Coppercompounds Copperturnings Arsenic and iron
Zinc compound Zinc metal or zinc
oxide
Aluminum, copper,
manganese,Mg, arsenic,
iron and nickel.
Therefore, proper measures should be taken to ensure the purity of raw materials
used in the manufacture.
Method / process of manufacture:
Manufacturing process involves various reactions carried out in single or multiple
steps. Starting from the raw materials used, equipment, reactions, intermediates
produced, solvents employed to the status of completion of the reaction, every
aspectserves as the source of impurity. These are explained as follows.
Starting materials or reagents used:
Many reagents are used in the process of manufacturing a product. If the products
are not washed properly to remove excess reagents, then these reagents are liable
to be carried as impurities to the final preparation.

4. 4
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Examples:
Calcium carbonate is prepared from the reagents calcium chloride and sodium
carbonate. Hence, calcium carbonate by this process is associated with alkali
(Na2CO3) and soluble chlorides. If the CaCO3 product is not washed properly to
remove excess of Na2CO3and chlorides, then they get carried as impurities. Due to
this reason, pharmacopeia has prescribed limits for soluble chlorides and alkali for
CaCO3.
CaCl2 + Na2CO3 CaCO3 + 2NaCl
In the synthesis of ammoniated mercury, dilute ammonia solution and mercuric
chloride solution are used as reagents. Proper washing of the end product
(ammoniated mercury) with cold water renders it completely free from impurities
(ammonium hydroxide).
HgCl2 + 2NH4OH NH2HgCl + NH4Cl + 2H2O
Reagentsemployed to eliminate other impurities:
In some manufacture process certain reagents are used to remove impurities
present in the final product, these reagents if not carefully used are liable to get
carried to the end product.
Example:
Barium is employed to remove excess sulphate in the synthesis of potassium
bromide. Improper usage results in the presence of very small amounts of barium
in the final product.

5. 5
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Solvents or vehicles used in the manufacturing
Water is the most commonly used solvent in many preparations. However, water
serves as a sourcefor many impurities.
Type of water Impurities present
Tap water Calcium, magnesium, sulphates, chlorides, sodium and
carbonates
Softened water Sodium and chloride
Demineralized water Organic impurities
Distilled water No impurities
Tap water is the cheapest solvent available but it contains many impurities.
Therefore, washing the final product with tap water leaves it with traces of
impurities and sometimes even adding additional impurities. Softened water is
prepared by passing tap water through sodium form of zeolite, such that sodium
ions from zeolite are exchanged for calcium and magnesium. However, sodium
and chlorine may get incorporated into the final preparation.
Demineralized water is prepared by passing tap water through the coloumn of ion –
exchange resins. All the impurities present in tap water except organic impurities
get eliminated. Therefore, in those preparations where demineralized water has
been used, the final productis liable to contain organic impurities.
Distilled water is free from both organic as well inorganic impurities but it is very
expensive. Hence, its use is limited.

6. 6
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Equipmentused in the process of manufacturing
Equipments or reactions vessels employed in the manufacturing process are made
of glass, tuber, metals or their alloys. The material of the equipment may react with
the reagents and solvents used in the process of manufacturing and contribute to
impurities in the end product.
Material of the equipment Impurity
Iron Arsenic
Galvanized iron Zinc
Sodaglass Alkali
Stream or waste pipe lead
In order to control the impurities arising from chemical reactions between the
solvents, reagents or both with the reaction vessel, vessel made from hard inert
glass like pyrex – borosilicate glass should be used. However, its high cost limits
its use.
Intermediatesgenerated during the synthesis
Most of the preparations involve generation of intermediates. If these intermediate
products are not completely converted into the final product, they get incorporated
as impurities.
Example:
In the preparation of potassium iodide ( KI) from potassium hydroxide and iodine,
potassium iodate (KIO3) is formed as an intermediate. KIO3 is evaporated to
dryness and the residue obtained is heated with charcoal to get KI. Incomplete or

7. 7
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
improper conversion of KIO3 is liable to be carried as an impurity to the final
preparation which is desirable.
6KOH + 3I2 5KI + KIO3 +3H2O
KIO3 + 3C KI + 3CO
Chemicalmethods used in the manufacturing process:
A substance or a reagent is subjected to a variety of chemical reactions during the
manufacturing process. The type of chemical reactions like halogenations,
oxidation, reduction, nitration, hydrolysis etc., employed may also contribute to the
presence of impurities in the final preparation.
Example:
Potassium iodide is synthesized from kelp (ash of a sea weed). When sea weed
containing nitrogenous organic matter is heated at very high temperature in the
presence of alkli, cyanides are generated. These cyanides may get incorporated as
an impurity.
Defects in the process of manufacturing
Synthesis of a compound should be carried out under appropriate conditions along
with correct measures of preparation. Improper mixing, incompleteness of the
reaction, inappropriate temperature, preasure and pH conditions yield compounds
with impurities.

8. 8
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Examples:
Synthesis of calcium chloride involves addition of pure calcium carbonate to
slightly excess quantity of dilute hydrochloric acid with continuous stirring
followed by filtration and concentration of filtrate to give CaCl2 crystals.
If the ingredients are not mixed properly or if any amount of HCl passes through
the filter or if the concentration is not properly carried out, then it affects the final
product.
CaCO3 + 2HCl CaCl2 + H2O + CO2
Manufacturinghazards:
Hazardous and toxic substance such as dust, paints, fuel or chemicals present in the
work place are capable of causing harm to the pharmaceutical products. The
manufacturer should provide analytical procedure to limit such impurities. The
manufacturing errors may go unnoticed. These are typical errors that occur due to
microbial contamination, particulate contamination etc. specifications and
analytical procedures are employed to estimate the identified or unidentified
impurities and also to include limits for impurities.
i. Arbitrary inclusion of particulatematter:
The hazardous substance such as dirt, glass, metallic ions, porcelain, plastic
fragments found during the operations like granulating, tabletting or in equipment
like sieves, filling machines, product container etc., may be accidentally introduced
into the pharmaceutical products.
Example:

9. 9
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Eye ointments packed in metal tubes made up of tin, aluminum generally get
contaminated due to the extrusion of metal particles from the packing material. The
extent of contamination depends upon the viscosity of the ointment. As the
viscosity of the ointment increases, the extent of extrusion increases.
ii. Arbitrary inclusion of microorganisms:
Almost all the pharmaceutical preparations may undergo microbial contamination
during the process of manufacture or during storage. Generally raw materials
obtained naturally are more prone to microbial contamination. Therefore to control
it, sterility tests should be performed on all the products, mainly upon liquids or
creams applied on the mucous membranes or broken skin, opthalamic and
parenteral preparations.
Materials Free from
Acacia, senna, and tragacanth Salmonella
Gelatin, pancreatin, starch, cochineal Salmonella and E.coli
Al(OH)3 gel, dried Al(OH)3 gel and
aluminum phosphate gel
pseudomonas
iii. Cross contamination:
When large quantities of powders, granules and tablets are handled, a substantiate
amount of air borne dust generates. If it is not properly controlled, it leads to cross
contamination of the products.
Precautions
The use of face masks or special equipment help to curb impurities occurring by
cross contamination.

10. 10
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Conditions of storage:
Storage conditions determine the efficacy and stability of the product. Requirement
of storage differ from one drug to the other. Various factors like material of the
container temperature, reactions taking place in the product., affect the final
preparation during the storage.
a) Carless storage:
Pharmaceutical preparations behavior when not stored properly.
Example:
Ferrous sulphate should be stored in air tight containers. Improper storage leads to
the conversion of soluble ferrous sulphate to insoluble ferric oxide in the presence
of air and moisture.
b) Filthy matter:
Dust particles, microorganisms, insect excreta etc., may affect the final
preparations. Novel packing techniques available inhibit contamination of the end
product, but raw materials are more likely to be attacked by filth during storage.
c) Effect of container materials
Pharmaceutical preparations when stored in inappropriate containers react with the
material of the containers undergo deterioration.
Examples:
Salicylic acid reacts with metal tubes, therefore, it should not be stored in metal
tubes unless and until they are lacquered internally.

11. 11
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
Atropine sulphate injection should be strictly packed in glass ampoules as it offers
hydrolytic resistance.
Therefore, a container should be so selected such that it is suitable for storing the
preparation and does not contribute to its degradation.
There are grades of glass containers available.
Type I: it exhibits very high hydrolytic resistance. It is a neutral glass.
Type II: it is formed by the surface treatment of glass and exhibit very high
hydrolytic resistance.
Type I and II glasses can be differentiated from each other by crushed glass test.
Type III: it possessesvery limited hydrolytic resistance.
Aqueous solutions of injections should be stored in either type I or II glass
containers while non – aqueous solutions as well as injectable solids are stored in
type III glass containers after complying with the test for hydrolytic resistance.
4. Atmospheric / environmental conditions:
Atmospheric conditions during manufacturing process as well as during storage
affect the quality of the final preparation.
Example: if sodium hydroxide is exposed to air for very long periods during the
process of manufacturing it reacts with carbon dioxide and gets converted to
sodium carbonate. This sodium carbonate gets incorporated into NaOH and serves
as an impurity.
2NaOH + CO2 Na2CO3 + H2O

12. 12
Punatipharma
Sree Dattha Institute of Pharmacy LingeswaraRao.Punati
Ph.D
5. Packing Errors:
Crystal packing of solids may lead to serve reactions which may affect the
preparation. Pharmaceutical products having same physical appearance i.e., size,
shape, colour, if packed in same type of containers may lead to packaging errors.
This leads to mislabeling of the products. Therefore handling similar type of
products at the same time should be avoided.
6. Deliberate adulteration or international substitution
Substitution of a pure product spurious, cheap, inferior, defective or toxic
substance is termed as adulteration. Accidental adulteration can be prevented by
storing away from harmful substances separately from purified substances.